The present invention relates generally to an automatic speed control system for an automotive vehicle which controls the vehicle speed at a desired or pre-set value. More specifically, the invention relates to an automatic vehicle speed control system capable of preventing the vehicle from accelerating unexpectedly to return the vehicle speed to the set value after the control operation thereof has been interrupted and the vehicle has been decelerated by the application of the brake or the release of the clutch.
As is well known, various automatic speed control systems have been developed and proposed for mechanically, electrically or electronically controlling the vehicle speed to a desired value. For driving the vehicle at a constant speed, the desired speed is set into the control system and the control system controls the vehicle speed to reduce the difference between the actual vehicle speed and the pre-set speed to zero. One means provided is that whereby the control system is operated by the driver to set a desired vehicle speed. The set speed is stored as an analog signal to be compared with a signal indicative of the actual speed. According to the difference between the set speed and the actual speed, the control system automatically controls vehicle acceleration ion. In the automatic speed control system, a restart switch is provided which is operated when the vehicle is returned to the controlled mode after the control operation is interrupted by applying the brake or releasing the clutch.
When the restart switch is operated, the vehicle is immediately accelerated to return it to the set speed. There is a disadvantage in the conventional control system, in that if the restart switch is damaged and cannot be turned off, the vehicle is accelerated as soon as the brake is released or the clutch is engaged. This could be dangerous since the driver may not intend to accelerate immediately.